High T/sub c/ superconductivity in the Ba/sub x/Y/sub 1-//sub x/CuO/sub 3-//sub y/ series

We have investigated various compositions of the Ba/sub x/Y/sub 1-//sub x/CuO/sub 3-//sub y/ system; experimental results showed high and sharp superconducting transitions both in ac susceptibility and resistance. Zero resistance above 90 K and resistive transition widths of about 3 K were found in a wide range of compositions, 0.50≤x≤0.80. For x below 0.50, the midpoint temperature of resistive transitions (T/sub c//sub 1/2/) was monotonically increasing with x. All onset chi-transition temperatures by ac susceptibility measurements were close to those of R-transitions. X-ray analysis showed that the single-phase compound corresponds to a nominal composition Ba/sub 0.65/Y/sub 0.35/CuO/sub 3-//sub y/. The other compositions of x = 0.50, 0.60, 0.70, 0.75, and 0.80 are not pure single-phase compounds. Single-phase oxygen defect-perovskite orthorhomic structure always exhibits high T/sub c/1 superconductivity